Anatomy of the Human Eye We often take our eyes for granted, but the human eye is quite a complex structure. Do you know how your eyes see?By Dennis Thompson, Jr. Medically reviewed by Lindsey Marcellin, MD, MPHThe human eye is a complex miracle of nature that provides us the power of eyesight, the ability to observe the world around us in all its beauty and intricacy.

The human eyeball is capable of producing detailed three-dimensional images in color. It is self-focusing and can switch from making out the tiniest of fine print to observing a faraway mountain peak in less than a second. It is made of water, jelly, and protein. The eyeball consists of these parts: · Sclera.. The sclera is often referred to as the "whites of your eyes," the tough white tissue that covers most of your eyeball. Muscles attached to the sclera move your eyes around.· Cornea. This transparent cup covers the part of your eye that takes in light. Think of the cornea as a window through which eyesight is possible.· Iris. This is the part of your eye with a ring of color, be it blue, green, hazel, or brown. The iris sits underneath the cornea and can contract or relax to control the amount of light entering your eyeball.· Pupil. The pupil is the round black hole located in the center of the iris and covered by the cornea. Light goes into the eyeball through the pupil, allowing eyesight. The pupil can enlarge or become smaller due to the muscles of the iris.· Lens. The lens is another transparent piece of tissue, like the cornea. The lens is located behind the pupil, and its job is to help focus light onto the back of the eyeball. Ciliary muscles attached to the lens can change its shape, allowing you to change the focus of your vision.· Vitreous gel. This clear, jelly-like substance fills up the inside of the eyeball and helps it maintain its shape.· Retina. This tissue located on the back wall of the eyeball contains millions of photosensitive cells known as rods and cones. Rods perceive black, white, and shades of gray, and work to maintain eyesight in low light. Cones distinguish colors, and are helpful for taking in fine details and maintaining eyesight in bright light.· Optic nerve. This bundle of more than one million nerve fibers takes the signals gathered by the rods and cones of the retina and transmits them to the brain, where they are translated into the constant stream of images that make up human eyesight. 5 Simple Ways to Protect Your EyesightYour eyesight rests on the health of your eyeballs. Here are a few ways to protect your sight: · Get regular eye exams. The only way to make sure your eyesight is 100 percent is to have regular eye exams from an optometrist or ophthalmologist. These eye care professionals also can detect health problems that could harm your eyesight if left untreated.· Wear sunglasses. Exposure to ultraviolet rays from the sun can damage your eyeballs, particularly the lenses, and cause cataracts later in life. Sunglasses designed to screen out UV rays help to protect your eyesight.· Wear safety glasses or goggles. These can protect your eyes when you're playing sports or performing activities during which debris or chemicals could fly into your eye.· Eat right. A diet rich in fruits, vegetables, and omega-3 fatty acids has been shown to contribute to overall eye health. Staying at a healthy weight also can help preserve your eyesight, as obesity can lead to systemic illnesses, such as diabetes, that can harm your eyes.· Don’t smoke — or stop smoking now if you do.Smoking has been linked to cataracts, damage to the optic nerve, and age-related macular degeneration, a condition which can lead to loss of vision. Given the complexity of the eye, ensuring your eyesight through regular visits to a medical professional is an important part of maintaining your overall health.